Pressure/vacuum transducers are known. Such devices typically couple to a source of pressure or vacuum; generate an electrical characteristic that varies according to the pressure or vacuum; and provide an electrical representation of the varied electrical characteristic such that the vacuum or pressure can be known to an operator, or other parts of the process.
High purity pressure or vacuum transducers are a relatively small subset of general vacuum or pressure transducers. These devices are specifically adapted for exposure to extremely delicate and/or very clean processes. These are the types of processes where a particle breaking from the pressure transducer or even-outgassing therefrom could have a deleterious effect on an entire processing line. One example of such an application is semiconductor processing.
Vacuum transducers are used for high purity applications involving, for example, the deposition or removal (etching) of materials, such as in the semiconductor industry. One concern when operating vacuum transducers in semiconductor deposition chambers is the accumulation of deposition material on the pressure sensor itself. In such applications, it has generally been known to employ a “plasma shield” to limit deposition onto the sensor. This has typically been accomplished by using a perforated piece of sheet metal, which is then spot welded to the housing in front of the sensor. This type of shield has several undesirable side effects. First, due to the thin cross-section of material, thermal conduction of the shield is poor. This poor thermal conduction can decrease the efficiency of heating systems that attempt to maintain the sensor and shield at elevated temperatures in order to reduce the accumulation of deposition material. Accordingly, the poor thermal conductivity of the shield may lead to premature deposited process material on the shield. Another undesirable side effect is that the shield will typically have many narrow, deep crevices at its attachment point to the sidewalls. These trapped volumes lengthen the “pump-down” times and present cleaning difficulties. Yet another undesirable side effect is that the typical sheet-metal shield is often very thin offering limited physical protection for the sensor. Due to its relatively poor physical robustness, the shield can sometimes break or generate particles that are undesirable in the extremely clean environments with which the sensors are employed.